Ip multimedia functionality identification

ABSTRACT

A wireless communication network is disclosed having a circuit switched network architecture and a packet switched network architecture, at least part of the packet switched network architecture supporting IP multimedia functionality, wherein the support of IP multimedia functionality is identified in a pre-registration communication between a user and the network.

FIELD OF THE INVENTION

The present invention relates to the mobile equipment supportinginternet protocol multimedia functionality in a packet switched network.The invention relates particularly, but not exclusively, to a GPRSnetwork.

BACKGROUND OF THE INVENTION

In packet switched wireless communication systems, such as GPRS (GeneralPacket Radio Service) networks, certain networks or parts of networkssupport internet protocol multimedia functionality. Thus mobileequipment which also supports such functionality, and which registerswith such a network, may utilise multimedia applications. The network orpart of the network that provides IP Multimedia functionality isreferred to as the IP Multimedia Subsystem (IMS).

In the GPRS network structure packet switched network coverage overlayscircuit switched network coverage, such that packet switched networkcoverage is provided in areas of the circuit switched network coverage,but coverage is not so comprehensive. As such, mobile equipment may bein an area provided with circuit switched network coverage but not withpacket switched network coverage. Still further, not all packet switchednetworks, or parts thereof, provide IP multimedia functionality. As sucheven when packet switched network coverage is available, IP multimediaservices may not be.

In current GPRS systems, the information provided in the broadcastcontrol channel (BCCH) includes a local area code (LAC) identifying thecircuit switched network and a routing area code (RAC) identifying thepacket switched network. If there is no routing area code in thebroadcast control channel, then obviously the mobile equipment canreadily identify that no packet switched services exist, and as such noIP multimedia services are supported. The user equipment may then simplyregister with the circuit switched network for voice connections.

However, if the broadcast control channel does include a routing areacode, then this is indicative of the availability of a packet switchednetwork. However, the existence of the packet switched network providesno indication in itself as to whether IP multimedia functionality isavailable in that packet switched network.

In accordance with current GPRS networks, in order to determine whetherIP Multimedia functionality is supported by the packet switched network,it is necessary to register with the network. In order to register withan IMS offering IP Multimedia functionality, the mobile equipment firstperforms a GPRS attachment, and then activates a packet data protocol(PDP) context or contexts. Thereafter, the user equipment must perform aCSCF discovery procedure. In the discovery procedure, the user equipmentreceives an address of a CSCF to which an IMS registration must be sent.An IMS registration may, for example, be a session initiation protocol(SIP) registration. Only when performing PDP context activation or CSCFdiscovery procedure, the user equipment is notified if the packetswitched network does in fact not support IP multimedia functionality.

Thus, in existing GPRS services, the user equipment must register withthe packet switched network before registration with an IMS can beattempted. Therefore there is a requirement to utilise a large amount ofsignalling, at the end of which it may be identified that IP multimediaservices are not available.

It is an aim of the present invention to overcome the above statedproblems. It is particularly an aim of the present invention to providean improved technique for determining the availability of IP multimediafunctionality in a network.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a method ofindicating the functionality of a packet switched wireless networkcomprising transmitting, in a pre-registration communication, anindication of the IP Multimedia functionality of the packet switchednetwork.

The pre-registration communication is a communication sent prior toinitiation of the registration. Thus, in accordance with the presentinvention, before the registration is complete (i.e. pre-registration)the network sends a specific message to a wireless terminal includinginformation of the services.

In this way, the invention allows a user to establish the existence ofIP multimedia services without any need to attempt to attach to a GPRSnetwork and activate a PDP context. In this way packet switched networkresources are utilised more efficiently and also a user equipment canselect an appropriate PLMN more rapidly.

The basic functionality offered by the network may be IP transportfunctionality, and IP multimedia functionality may be optionallyavailable.

The availability of optional functionality may be indicated in abroadcast control signal. The functionality may be indicated in atransmission by the packet switched network identifying itself. Thetransmission may include a routing area code. The transmission mayinclude packet data protocol context.

The method may be utilised in a GPRS network. The transmission mayinclude a GPRS attach.

The invention further provides a wireless communication network having acircuit switched network architecture and a packet switched networkarchitecture, at least part of the packet switched network architecturesupporting IP multimedia functionality, wherein the support of IPmultimedia functionality is identified in a pre-registrationcommunication between a user and the network.

The pre-registration communication may comprise a transmission fromradio access network to a user. The pre-registration communication maycomprise a broadcast.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example topology of a circuit switched networkover-layered with a packet switched network;

FIG. 2 illustrates an exemplary block level diagram of a system forimplementing the network topology of FIG. 1; and

FIG. 3 illustrates an example of the adaptation of the broadcast controlchannel of a network transmission in accordance with one embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described herein with reference to a particular,non-limiting example. The invention is not limited to such an example,and one skilled in the art will appreciate from the following thepossibilities for the more general application of the present invention.

Referring to FIG. 1 there is illustrated an example of a circuitswitched network coverage overlaid with areas of packet switched networkcoverage. The circuit switched coverage is generally illustrated by area2. The packet switched coverage is generally illustrated by areas 6 and4. Area 4 illustrates a packet switched area supporting IP multimediafunctionality. The packet switched areas may or may not support IPmultimedia functionality. In the example of FIG. 1 it is assumed thatcoverage area 4 supports IP multimedia functionality, and areas 6 donot. Further referring to FIG. 1 the square blocks 8 identify variousbase stations supporting the circuit switched network, and the circularblocks 10 identify the various base stations supporting the packetswitched network(s). The solid circular blocks 10 a represent basestations of a network supporting IP multimedia functionality, and thehollow circular blocks 10 b represent those that do not. User equipmentroams in the network, as represented by mobile stations 12. The mobilestation 12 c, as shown in FIG. 1, roams within the packet switchedcoverage area 4 of the base station 10 a.

The present invention relates to any network infrastructure or corenetwork providing coverage such that IP multimedia functionality isselectively provided. For the purposes of understanding the presentinvention, a particular example of a core network for supporting arouting area such as is shown in FIG. 1 is described hereinbelow withreference to FIG. 2. However, it should be understood that the inventionis not limited to such an example of a core network.

More particularly, the present invention may be implemented for anInternet Protocol Multimedia subsystem (IMS).

Referring to FIG. 2, there is illustrated in block diagram form the mainnetwork element components of a system for supporting a routing areasuch as area 10 a in FIG. 1. The user equipment 12 c interfaces with thebase station 10 a over the air interface (Uu). The base station isconnected to a radio network controller (RNC) 14 on the network side viaan interface Iub. The RNC owns and controls the radio resources withinits domain. The RNC 14 is connected to a core network 16 via interfaceIu. The main elements of the core network 16 are illustrated in FIG. 2.The core network includes, for circuit switched functionality, a mobileservices switching centre/visitor location register (MSC/VLR) 18connected to the Iu interface and a gateway mobile services switchingcentre (GMSC) 22, which in turn is additionally connected to externalcircuit switched networks 28. For packet switched functionality, thecore network includes a serving GPRS support node (SGSN) 20 connected tothe Iu interface and a gateway GPRS support node (GGSN) 24, which inturn is connected to external packet switched networks 30. All elementsof the core network 16 are additionally connected to a home locationregister (HLR) 26.

The circuit switched networks 28 provide circuit switched connections,such as ISDN and PSTN networks The packet switched external networksprovide connections for data packet services, such as the internet. Thedata packet services include, in the present example for the network ofFIG. 1, IP multimedia services.

The structure and operation of the network elements of the GPRSarchitecture illustrated in FIG. 2 are well-known to those skilled inthe art, and as such no further detail will be discussed herein.

The implementation of an IMS core network will similarly be familiar toone skilled in the art. The IMS comprises all the core network elementsfor provision of IM services. The entities of the IM subsystem includethe home subscriber server (HSS) and the call state control function(CSCF). The HSS contains subscription related information to support thenetwork entities handling calls/sessions. The CSCF can act as aninterrogating CSCF (I-CSCF), a proxy CSCF (P-CSCF) or a serving CSCF(S-CSCF). The P-CSCF is the first point of contact for a UE within theIMS. The S-cscf handles the session states in the network. The I-CSCF ismainly the contact point within an operator's network for allconnections destined to a subscriber of that operator network. As statedhereinabove, the present invention is not limited to any particularnetwork implementation, and the examples given herein are for thepurposes of illustrating the broad applicability of the presentinvention.

All base stations 8, 10 a and 10 b of the network arrangement shown inFIG. 1 transmit information via a broadcast control channel (BCCH) whichis used by user equipment within their domain. When user equipmentdecodes the information from the broadcast control channel of aparticular base station, it uses the information, for example, todetermine whether to connect to the network using the base station fromwhich the broadcast control channel was received.

In current GPRS networks, the broadcast control channel includes thelocation area code for supporting circuit switched communication, andwhere appropriate the routing area code for supporting packet switchedcommunication. As such the user equipment is able to determine, inaccordance with whether circuit or packet switched network functionalityis required, whether to connect to the network.

In accordance with the present invention, the broadcast control channelof a network element is adapted to further include an indication as towhether the packet switched network supports IP multimediafunctionality.

In the preferred embodiment of the present invention, for a GPRSimplementation, the core network (CN) packet switched domain specificGSM-MAP NAS system information element transmitted in the broadcastcontrol channel is modified in order to implement the present invention.This two octet element is specified in 3GPP TS 24.008 version 5.x.x. Thecontainer and actual message in which this information is sent to the UEis specified in 3GPP TS 25.331.

The modification of this element is shown in FIG. 3.

The length of this element, as shown in FIG. 3, is two octets. The firstoctet 50, as is known in the art, contains the eight-bit field of therouting area code (RAC) 58. This field is the binary representation ofthe routing area code. Bit 8 in the first octet is the most significantbit.

The second octet 52 of this element contains the network mode ofoperation (NMO) field 54, which is a 1 bit field, in the leastsignificant bit position. As known in the art, the setting of this fielddefines the network mode of operation. If the field is set to 1, networkmode of operation II is set. If the field is set to 0, network mode ofoperation I is set.

The second octet of this element also contains, in accordance with anembodiment of the present invention, an internet multimedia support(IMS) field 56, which is also a 1 bit field, in the second leastsignificant bit position. The setting of this field is the binaryrepresentation of the internet multimedia support. In this embodiment ifthe bit is set to 1, then this indicates that there is no internetmultimedia support provided in the network. If the bit is set to 0, thenthis indicates that there is internet multimedia support in the network.It should be noted that this is an example implementation, and inpractice the setting of the bits may be reversed, e.g. with bit set to 1to identify internet multimedia support.

The bits 3 to 8 of the second octet, referenced as 60, are all spare,and are all preferably set to 0. The IMS field may alternatively beprovided in any of the other spare bit positions of the second octet,and the indication of the 0 or 1 setting of the bit may be similarlyreversed as discussed above.

Thus in accordance with the preferred embodiment of the presentinvention, the user equipment is able to identify through the broadcastcontrol channel whether the network supports IP multimedia functionalityat the same time that the presence of a packet switched network isidentified. As such the signalling associated with user equipmentlooking to locate IP multimedia functionality is significantly reduced,as there is no requirement for the user equipment to perform unnecessarysignalling connection establishment, GPRS attach, and PDP contextactivation attempts if the network does not support IP multimediaservices. In addition, in the absence of IP multimedia functionality,the user equipment may connect directly to the mobile services switchingcentre in order to obtain voice services, rather than using up packetswitch resources, if only voice services are required in the absence ofany IP multimedia functionality.

It should be understood that the provision of information concerning theavailability of IP multimedia functionality in accordance with thepresent invention, as discussed hereinabove, is only one possible way ofproviding such information. For example, the information may be conveyedin the GPRS attach or PDP context activation. However, these proceduresmay not have all the advantages of the preferred embodiment describedherein as they require the user equipment to attach/activation before itis known whether the service is available.

It will be further understood by one skilled in the art that theinvention is not limited in its applicability to GPRS networks. Theinvention may also be advantageously utilised in UMTS (universal mobiletelecommunications services) terrestrial radio access networks. Thespecific implementation of the principles of the invention in such analternative environment will be well within the scope of one skilled inthe art.

Thus although the invention has been described herein with reference toparticular embodiments and examples, it will be apparent that theapplicability of the invention is significantly broader than thatdisclosed. One skilled in the art will appreciate that modifications maybe made to the information provided herein whilst still remaining withinthe scope of the invention as defined by the appended claims.

1. A method of indicating the functionality of a packet switchedwireless network comprising transmitting, in a pre-registrationcommunication, an indication of the functionality of the packet switchednetwork.
 2. A method according to claim 1 wherein the functionality isInternet protocol functionality.
 3. A method according to claim 2wherein the Internet protocol functionality is Internet protocolmultimedia functionality.
 4. A method according to claim 1 wherein thefunctionality is identified in a broadcast control signal.
 5. A methodaccording to claim 1 wherein the functionality is identified in atransmission identifying the packet switched network.
 6. A methodaccording to claim 5 wherein the transmission includes a routing areacode.
 7. A method according to claim 1 wherein the transmission includespacket data protocol context.
 8. A method according to claim 1 utilisedin a GPRS network.
 9. A method according to claim 8 wherein thetransmission includes a GPRS context.
 10. A wireless communicationnetwork having a circuit switched network architecture and a packetswitched network architecture, at least part of the packet switchednetwork architecture supporting IP multimedia functionality, wherein thesupport of IP multimedia functionality is identified in apre-registration communication between a user and the network.
 11. Awireless communication network according to claim 10 wherein thepre-registration communication comprises a transmission from the packetswitched network architecture to a user.
 12. A wireless communicationnetwork according to claim 10 wherein the pre-registration communicationcomprises a broadcast.